Question 1

Which of the following best explains why viruses are classified as nonliving microbes?

Accepted Answer

They cannot carry out metabolism or reproduce independently outside a host cell.

Question 2

A scientist discovers a new virus with a helical capsid and an envelope. Which of the following statements about this virus is most likely true?

Accepted Answer

It is an animal virus that acquires its envelope from the host cell membrane during budding.

Question 3

Which of the following best describes the process of antigenic drift in influenza viruses?

Accepted Answer

A gradual accumulation of mutations in the HA and NA spike genes.

Question 4

Why do RNA viruses generally evolve faster than DNA viruses?

Accepted Answer

RNA-dependent RNA polymerases lack proofreading ability, leading to higher mutation rates.

Question 5

A patient is diagnosed with a persistent viral infection characterized by periodic flare-ups and dormancy. Which type of infection is this?

Accepted Answer

Latent persistent infection

Question 6

Which of the following is a key difference between the lytic and lysogenic replication cycles of bacteriophages?

Accepted Answer

The lysogenic cycle allows the phage genome to be replicated along with the host cell's DNA without immediately killing the host.

Question 7

Which of the following best defines 'tropism' in the context of virology?

Accepted Answer

The types of cells and tissues a virus can infect within a host.

Question 8

A virus with a segmented RNA genome infects a host cell already infected by a different strain of the same virus. What is the most likely outcome?

Accepted Answer

Genetic reassortment may occur, potentially creating a new viral strain with mixed genome segments.

Question 9

Which of the following is a medically important consequence of phage conversion in bacteria?

Accepted Answer

Bacteria acquire new pathogenic properties, such as toxin production.

Question 10

Which of the following best describes the structure of a naked virus?

Accepted Answer

A protein capsid surrounding the genome, without a lipid envelope.

Question 11

A virus has a single-stranded negative-sense RNA genome. What must occur before its proteins can be synthesized by the host cell?

Accepted Answer

The genome must be transcribed into complementary mRNA by an RNA-dependent RNA polymerase.

Question 12

Which of the following is a characteristic of prions?

Accepted Answer

They are infectious proteins that cause misfolding of normal cellular proteins.

Question 13

Which of the following viruses is associated with the development of cancer in humans?

Accepted Answer

Human papillomavirus (HPV)

Question 14

During the release stage of animal virus replication, which of the following is true for enveloped viruses?

Accepted Answer

They are released by budding from the host cell membrane, acquiring their envelope in the process.

Question 15

Which of the following equations best represents the relationship between the number of new virions produced ($N$), the number of infected host cells ($C$), and the average burst size per cell ($B$)?

Accepted Answer

$N = C 	imes B$

Question 16

A patient presents with symptoms of Creutzfeldt-Jakob disease (CJD). Which of the following is the most likely cause?

Accepted Answer

A misfolded prion protein inducing misfolding in normal proteins

Question 17

Which of the following best describes the process of reverse transcription in retroviruses?

Accepted Answer

Conversion of viral RNA into DNA by reverse transcriptase

Question 18

Which of the following is a correct statement about the host range of a virus?

Accepted Answer

It is the spectrum of host species a virus can infect, which may change due to mutations.

Question 19

Which of the following steps is unique to the replication of enveloped animal viruses compared to naked animal viruses?

Accepted Answer

Penetration by membrane fusion

Question 20

A virus is classified as a double-stranded DNA virus. Which of the following best describes how it produces mRNA for protein synthesis?

Accepted Answer

Its DNA is transcribed into mRNA by host RNA polymerase.

Viruses and Prions: Structure, Classification, and Replication

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